Case Study 

Case Study (1)
A Remote Sensing-GIS evaluation of urban expansion and its impacts on surface temperature in the Zhujiang Delta, China

PROBLEM DESCRIPTION

The Zhuijang Delta of South China has experienced a rapid urban expansion over the past two decades due to accelerated economic growth. In the coastal region such as the Zhujiang Delta massive agricultural land is disappearing each year, converting to urban
use. Changes in land cover include changes in bio diversity, actual and potential primary productivity, soil quality, run over and sedimentation rates (Steven et al. 1992), and cannot be well understood without the knowledge of land use change that drives them. (1) This change in the land use pattern has its environmental impacts. It has a great impact on climate. The land covered by building, roads and such other impervious layers, which leads to the high solar radiation absorption, and a greater thermal capacity and conductivity, so that heat is stored during the day and released in the night. Hence the urban areas have higher temperature than the surrounding rural areas. This thermal divergence, in conjunction with waste heat released from urban houses, transportation and industry, contribute to the development of urban heat. (1)

STUDY AREA

The study area, the Zhuijang Delta is located between latitudes 21°40’ N and 23° n and longitudes 112° E and 113° 20’ E. It is the third biggest river delta in China and has an area of 17,200 sq. km. The study area covers 15 cities or counties: Guangzhou, Panyu, Sanshui, Nanhai, Foshan, Shunde, Jiangmen, Zhongshan, Zhuhai, Xinhui, Doumen, Zengcheng, Dongguan, Baoan and Shenzhen. The Delta has a subtropical climate with an average annual temperature between 21  to 23 degrees Celsius. The 80% of rainfall comes between April and September. This region is the largest area of economic concentration in South China. Hong Kong and Macao are also located in this region, which results in dramatic economic expansion. The rapid economic development has brought about fundamental changes in land use and land cover patterns. The integrated approach developed in this paper is to analyze the changing patterns of urban land use/cover and its impacts on surface temperature.


          

  Map of the study area


METHODOLOGY

Integration of GIS and remote sensing were applied to study the impact of urban growth and the surface temperature. Land use/cover patterns for 1989 and 1997 were mapped by using Landsat Thematic Mapper. Seven land use types were identified: urban or built up area, barren land, crop land, horticulture farms, dike-pond land, forest and water. Erdas image computer software was used to enhance the Landsat image in histogram to increase the volume of visibility. Quantitative aerial data of the overall land use changes as well as gains and losses in each category between 1989 and 1997 were complied. In order to analyze the nature, rate and location of urban land change, an image of urban and built up land was extracted from each original land use image. This helped to obtain an urban land change image by overlaying and recoding the images. These images are again overlaid with several geographic reference images to help to analyze the patterns of urban expansion, including an image of the county/cities boundary, major roads and major urban centers. This helped to understand the points or locations of urban sprawl.

The change in the surface temperature was determined by using remote sensing. The 1.1 km. spatial resolutions of these data were found suitable for small scale urban temperature mapping. The much higher resolution of 120m were used seldom to derive the surface temperature. Models were used to review the change in the surface temperature from 1989 to 1997. This image of surface temperature change were made and then overlaid with land use map to study  how all there changes have interacted.

RESULTS AND DISCUSSIONS

There has been change in the land use from 1989 to 1997., the built up land and horticulture farm land has increased while the barren land, crop land and forests have decreased. The maps below show the urban expansion and relative increase in temperature. These results obtained with the use of GIS and Remote sensing can be used for the analysis of policy developed to deal with urban sprawl like at what locations green belt should be developed and it will also help us to identify the constraints like the built up area for developing specific objective related policy.


  
The urban expansion map of the Zhuijang Delta region



 

Spatial distribution of temperature increased zones, 1989 to 1997

1. “Application of  GIS in major Urban Planning projects in Netherlands” – by: Marjan Bevelender

  

 

 

 

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